Acrylonitrile polymer composition stabilized with formaldehyde, a phosphate, and an inorganic acid and method of making same



United States Patent Ofiice 2,878,218 Patented Mar. 17, 1959 2,878,218 ACRYLONIT-RILE POLYMER COMPOSITION sm BILIZED WITH FORMAILDEHYDE, A rnos- PHATE, AND AN INORGANIC ACID AND METH- OD OF MAKING SAME Lloyd T. Jenkins, Decatur, Ala andRicliard R. Holmes,

Bethesda, Md., assiguors ration, Decatur, Ala, a corporation of Delaware No Drawing. Application May 23,1956 Serial N0. 586,674

18 Claims. (Cl. 260-326} This invention relates to the stabilization of acryloni= trile polymers and blends thereof. Moreparticula'rly, it relates to the stabilization of acrylonitrilepolymers and" blends thereof which have a tendency to develop color ployed to etiectsolutions, from which shapedarticles are to be formed, a tan to velops in the solutions the productformed therefrom. This color also develops in solutions upon standing forprolonged periods oftime'.

dark brown color frequently de- Themechanism which causes color formationliasnot beendefinitely ascertained, therefor have been advanced. The presence of" metal although a variety of reasons" ions, suchas iron, copper andman'ganese in the solutions may cause the color. The employment of amide compounds as solvents may result in formation of amines when heat is appliedandcausecolorin the compositions.

Impurities present inthesolvents' have also" been cited as a cause. formation, it

Whatever may be the reason for color results in compositions. and products of undesirable standards and therefore, hasbeen thesource: of concern, particularly in commercial operations where such types of polymers or copolymers are employed.

Accordingly, it is an objectof the present invention to prevent undersirable color formation in; acrylonitrile, polymer compositions.

Another object is to minimize color formation when" solutions of the acrylonitrile polymers are permitted to claims, is intended to include hmopolygenerally insoluble in the more com- In those instances where suitablesolvents 1 and therefore is carriedoveriiito' a) The Cliemstrand Corpoweight of the polymer. percent by weightof, polymerized or 2 reagent comprising formaldewherein R is sodium or a cresyl radical; nd an inorganic a-cid havingt an ionization constantgreater than 1- -10- The components of the inhibiting agent may be employedin equal or unequal amounts, any one constituent Being: present in a range of from 98 to 1 percent ina three; component system. The total amount of inhibiting agent may be employed in a rangeof about 03m 15 percent, based on the total polymer weight. However, it is preferred that the inhibiting agent of theinstant invention be present in a small amount comparedto the amount of polymer dissolved. Thus, although the amount is not critical, it is preferred that the inhibiting agentbepresent' in the amount of about 0.3 to 3 percent, based onthe total The inhibiting agent may be added to the solvents before or after the polymer is dissolved therein. The inhibiting agent permits exposure to high temperatures for prolonged standing periods with out the development of the objectionable color which usually results in, such solutions. The compositions of the instant invention may be prepared in avarying: temperature range. For example, the compositions of the instant invention may be prepared by mixing the polymer, 2. suitable solvent and the inhibiting agent at any tern peraturev orheating the mixture to a temperature up to the boilingpoint of the solvent.-

, Among the compounds bearing the general Formula I which' may be employed in practising: the instant inventionare trisodium phosphate, tri'cresyl' phosphate; etc.

, dimethylacetamide, aqueous Amongthe acids having, an ionization constant greater than 1 instant inventionare sulfuric acid, nitric acid, phosphoric acid; hydrochloric acid, etc.-

Among the solvents which may beused in practising the instant invention are N,N-dimethylformamide; N,N- zinc chloride, sulfuric acid, aqueous nitric acid, aqueous sodium thiocyanate, ethylone carbonate, sulfolane,- nitrometharie, etc.

X10" which maybe employed in practising the The polymeric, materials, which maybe employed in thepractice of thepresent-invention, are polyacrylonitrile,

, copolymers, including binary and ternary polymers constand for a prolonged period of time or upon application It is also an object of formation in acrylonitrile tui'es.

the invention to prevent color polymersat elevated temper-a A stillfurther object of the invention is the production:

of the invention are acco'm taining atleast 80 percentbyweigh'tof acrylonitrile in the or copolymers comprising acrylonitrile with from 2 to 50 .percent of another polymeric material, theblend having polymer molecule, or a, blend comprising-polyacrylonitrile an overall polymerized acrylonitrile content of at least 80 percent by weight. Whilethepreferred polymersemploy'ed in the instant invention are those containing at least 80 percentof acrylonitrile, generally recognized as the fiber-forming acrylonitrile polymers; it will be understood tli at the invention islik'ewise applicable to polymers containing less than 80 percentacrylonitrile andthesame" stabilityis realized withtheinhibiting'agents'defined herein The acrylonitrile polymer percent acrylonitrile are useful in forming films, coating compositions; moldmgoperations, lacquers, etc., in all of! which applications the alleviation of undesirable color is extremely important.

For example, the polymer may be'a copolymer of from to 98 percentacrylonitrile and from 2 to20fpercent" of "another monomer containing the C.'1C linkage" an containing less than 80 'copolymerizable with acrylonitrile. finic monomers include acrylic, alpha-chloroacrylic and methacrylic acids; the acrylates, such as methylmethacrylate, ethylmethacrylate, butylmethacrylate, methoxymethyl methacrylate, beta-chloroethyl methacrylate, and the corresponding esters of acrylic and alpha-chloroacrylic acids; vinyl chloride, vinyl fluoride, vinyl bromide, vinylidene' chloride, l-chloro-l-bromoethylene; methacrylonitrile; acrylamide and methacrylamide; alph'a-chloroacryla-mide, or monoalkyl substitution products thereof; methyl vinyl ketone; vinyl carboxylates, such as vinyl acetate, vinyl chloroacetate, vinyl propionate, and vinyl stearate; N-vinylimides, such as N-vinylphthalimide and N-vinylsuccinimide; methylene malonic esters; itaconic acid and itaconic ester; N-vinylcarbazole; vinyl furane; alkyl. vinyl esters; vinyl sulfonic acid; ethylene alpha, betadicarboxylic acids or their anhydrides or derivatives, such as diethylcitraconate," diethylmesaconate, styrene, vinyl naphthalene; vinyl -substituted tertiary heterocyclic amines, such as the vinylpyridines and alkyl-substituted vinylpyridines, for example, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine', etc.; l-vinylimidazole and alkyl-substituted l-vinylimidazoles', such as 2-, 4-, or 5- methyl-l-vinylimidazole, and other C=C containing polymerizable materials.

The polymer may be a ternary interpolymer, for example, products obtained by the interpolymerization of acrylonitrile and two or more of any of the monomers, other than acrylonitrile, enumerated above. More specifically, and preferably, the ternary polymer comprises acrylonitrile, methacrylonitrile, and 2-vinylpyridine. The ternary polymers preferably contain from 80 to 97 percentiofacrylonitrile, from 1 to percent of a vinylpyridine or a l-vinylimidazole, and from 1 to 18- percent of another substance, such as methacrylonitrile or vinyl chloride. 'I

, The polymer may also be a blend of polyacrylonitrile or of a binary interpolymer of from 80 to 99 percent acrylonitrile and from 1 to 20 percent of at least one other C=C containing substance with from 2 to 50 percent of the weight of the blend of a copolymer of from 10 to. 70 percent of acrylonitrile and from 30 to 90 percent of at leastone other C=C containing polymerizable monomer. Preferably, when the polymeric'material comprises a blend, it will be a blend of a copolymer of 90 to .98 percent acrylonitrile and from 2 to 10 percent of another mono-olefinic monomer, such as vinyl acetate, which is not receptive to dyestufi, with a sixthcient amountof a copolymer of from 10 to 70 percent of acrylonitrile'and from 30 to 90 percent of a vinylsubstitutediertiary h'eterocyclic amine, such as vinylpyridine or l-vinylimidazole, to give a dyc'able'blend having an overall vinyl-substituted tertiary heterocyclic amine content of from 2 to 10 percent, based on the weight of the blend.

The polymers, useful .in the practice of the present invention, may be prepared by any conventional polymerization procedures, such as mass polymerization methods, solution polymerization methods, or aqueous emulsion procedures. However, the preferred practice utilizes suspension polymerization wherein the polymer is prepared in finely divided form for immediate use in the fiber fabrication operations. The preferred suspension polymerization may utilize batch procedures, wherein mono mers are charged with an aqueous medium containing the necessary catalyst and dispersing agents. A more desirable method involves the semi-continuous procedure in which the polymerization reactor containing the aqueous medium is charged with the desired monomers and the continuous withdrawal of polymer may also be employed.

The polymerization is catalyzed by means of any water-soluble peroxy compound, for example the potassium, ammonium and other water-soluble salts of peroxy acids, sodium peroxide, hydrogen peroxide, sodium perborate, the sodium salts of other peroxy acids, and any Suitable monoole- 4 other water-soluble compound containing a peroxy group (O-O-). A wide variation in the quantity of peroxy compound is possible. For example, from 0.1 to 3.0 percent by weight of the polymerizable monomer may be used. The catalyst may be charged at the outset of the reaction, or it may be added continuously or in increments throughout the reaction for the purpose of maintaining a more uniform concentration of catalyst in the reaction mass. The latter method is preferred because it tends to make the resultant polymer more uniform in its chemical and physical properties.

, of emulsion stabilizers.

Although the uniform distribution of the reactants throughout the reaction mass can be achieved by vigorous agitation, it is generally desirable to promote the uniform distribution of reagents by using inert wetting agents,

Suitable reagents for this purpose are the water-soluble salts of fatty acids, such as sodium oleate and potassium stearate, mixtures of watersoluble fatty acid salts, such as common soaps prepared by the saponification of animal and vegetable oils, the amino soaps, such as salts of triethanolamine and dodecylmethylamine, salts of rosin acids and mixtures thereof, the water-soluble salts of half esters of sulfuricacid' and long chain aliphatic alcohols, sulfonated hydrocarbons, such as alkyl aryl sulfonates, and any other of a wide variety of wetting agents, which are in general organic compounds containing both hydrophobic and hydrophilic radicals. The quantity of emulsifying agents will depend upon the particular agents selected, the ratio of monomer to be used, and the conditions of polymerization. In general, however,'from 0.01 to 1.0 percent by weight of the monomers may be employed.

. ring devices are the most effective means of insuring the The emulsion polymerizations are preferably conducted.

in glass or glass-lined vessels which are provided with a means for agitating the contents. Generally, rotary stirintimate contact of the reagents, but other methods may.

be successfully employed, for example by rocking or tumbling the reactors. The polymerization equipment generally used is conventional in the art and the adaptation of a particular type of apparatus to the reaction contemplated is within the province of one skilled in the art. The articles manufactured therefrom may be produced by well-known conventional methods, for example, the wet-spinning, dry-spinning and melt-spinning methods for producing fibers.

The following examples are illustrative rather than limitative and all parts, proportions and percentages are by weight unless otherwise specified.

EXAMPLE I 7.5 grams of a polymer blend of 88 percent of a copolymer containing 94 percent of acrylonitrile and 6 percent of vinyl acetate and 12 percent of a copolymer of 50-percent of acrylonitrile and 50 percent of Z-methyl- 5-vinyl pyridine were added to 45 milliliters of N,N-dimethylacetamide containing approximately 0.05 gram of' titanium dioxide. The mixture was stirred and heated to 70 C. It was then quickly cooled to room temperature and the color measured. This sample was used as a control. The purity is set forth below. Subsequently, like samples were prepared but with 0.225 gram of a color inhibitor containing 0.075 gram each of formaldehyde, trisodium phosphate and sulfuric acid; formaldehyde, tricresyl phosphate and sulfuric acid. The purity is set emit ExAMPian:

grams tof: a copolymer containing 94 percent of acrylonitrile and 6- percent ofsvinyl acetate were added to" 45 milliliters of N,N-dimethylacetamide containing ap proximately 0.05 gram of titanium dioxide. The mixture was stirred and heated for 35 minutes at 70 C. It was then quickly cooled to room temperature and the color measured. This sample was used' as a control. The purity is set forth below. Subsequently, a like sample was prepared but with 0.225 grams of aninhibiting .agent'containing 01075 gram each of formaldehyde, .tricresyl phosphateand. sulfuric acid; Thepurityis set forth below;

T able III Inhibitor Percentage Purity" a I l Control--. 10.2 Formaldehyde, TricresylPhosphate and Suirurie Acid; 3 8. 4

EXAMPLE 111' 7.5grams of an acrylonitrile.homopolymer were added N,N-dimethylacetamide containing.

to 45 milliliters. of approximately 0.05 gram of titanium dioxide. Themixture was stirred and heated for 50 minutes at-90 C. It

was then quickly cooled to room temperatureand the color measured. This sample was used as a-control. Thepurity. of the controisarnple is set-forth below; Sub

sequently, like samples were prepared but 1 with v 0.225

gram of an inhibiting agent containing 0.075gram'ieach of -formaldehyde, trisodium phosphate and l sulfuric ;acid;. formaldehyde,.tricresyl phosphate and sulfuric acid: The

purity/is set forth.below.

The testsfor color indicative 'of approaching whitenessused-throughout the examples consistofmeasurements of purity as calculated from the tristimulus values determinednonv a 1GeneraliElectric spectrophbtometer by the methods recommended by. the- Standard Observer and Coordinate System of the International Commissionon lllumination, as fullyset forth in the Handbook. of byTheTechnology Press, Massa' Colorimetry published chusetts Institute of Technology in 1936.

The compositions of the instant invention present many advantages. For example, products formed from the polymer solutions of the instant invention are free of objectionable color and therefore of greater commercial value. In preparing the polymer solutions, heat may be applied without the danger of color formation and the solutions, if necessary, may stand for prolonged periods and remain free of color. The inhibiting agents are readily available and inexpensive. Therefore, no great increase in production cost is necessary. The compositions containing the inhibitors may be prepared without going through detailed and elaborate procedures that necessitate expensive changes in the design of the ap paratus used to manufacture them.

It will be understood to those skilled in the art that many apparently widely different embodiments of this invention can be made without departing from the spirit and scope thereof. Accordingly, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

We clairni i j 1. Anew composition of matter comprising-a prulynier containing at least percent of polymerized acrylonitrile and: up to. 20 'percent 'of another" polymerizable mono-olefinic monomer copolymerizable therewithgi a solventtherefor, and an inhibiting agent cor1taining5substantially equal proportions by weight of formaldehyde-:1:

a compound having fthe general formulae;

i R-OI =0 R wherein R is selected from the group consisting of sodium and cresyl radicals; and an inorganic acid having an ionization constant greater than 1 10" 2. A new composition of matter as defined in claim 1 wherein the polymer is a-;copolymercontainingfrom- 80 to 98 percent-of arcylonitrileand from 2 to20' percent of another polymerizable mono-olefinic monomer copolymerizable therewith.

3. Anew composition of matter as defined' inlclaim 1 wherein the polymer is a blend of-80 to -99-percent of (A) a copolymer-containing to 98- percentof acr y lonitrile and 2m 10 percent of vinyl acetate and 1 to 20 percentof 5 (B) a -copolymer containing! 10 to 70-- percent of 2-metliylpercent of acrylonitrile and 30 to 90 5-vinylpyridine. r

4. A new composition of matter as defined in claim 3 wherein the inhibiting agent contains formaldehyde, trisodium phosphate and sulfuric acid.

5. A new compositionof matter as defined in claim 1 wherein the polymer is polyacrylonitn'le.

6. A new composition of matter asdefined in claim 5 wherein the inhibitingagent contains formaldehyde,

trisoduim phosphate and sulfuricacid.

7. A newcomposition ofmatter as definedin claim 1 wherein the inhibiting agent contains formaldehyde;

81' A newecomposition of matter as defined in" claim 9. A new composition'of matter comprisinga polymer amine, said it blend having: an overall vinylasulistitutedi tertiary heterocyclic amine contentrof fronr 2=t0. 10=- percent basedon the weightof -the' blend, a: solvent therefor, andvan inhibiting; agent containingmsubstan tially equal proportions by weight of formaldehydeg'i a compound having the general formula,

wherein R is selected from the group consisting of sodium and cresyl radicals; and an inorganic acid having an ionization constant greater than 1X10".

10. A new composition of matter comprising a copolymer containing 30 to 98 percent of acrylonitrile and 2 to 20 percent of vinyl acetate, a solvent therefor, and 0.3 to 15 percent, based on the total weight of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal proportions by weight of formaldehyde, a compound having the general formula,

where R is selected from the group consisting of sodium and cresyl radicals; and sulfuric acid.

11.- A new composition of matter comprising a polymer'blend of 80 to 99 percent of (A) a copolymer containing 90 to98 percent of acrylonitrile and 2 to 10 percento'f vinyl acetate and 1 to 20 percent of (B) a copolymer containing 10 to 70 percent of acrylonitrile and .30 to 90 percent of 2-methyl-5-vinylpyridine, a solvent therefor, and 0.3 to 15 percent, based on the total weight of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal proportions by weight of formaldehyde, a compound having the general formula,

i l R-P=0 R wherein R is selected from the group consisting of sodium and cresyl radicals; and sulfuric acid.

13. A new composition of matter comprising polyacrylonitrile, a solvent therefor, and 0.3 to 15 percent,-

based on the total weight of the polymer, of an inhibiting agent, said inhibiting agent containing substantially equal proportions by weight of formaldehyde, a compound having the general formula,

RO-1:-"=O R-O wherein R is selected from the group consisting of sodium and cresyl radicals; and sulfuric acid.

14. A method for preparing a new composition of matter comprising mixing a polymer containing at least 80-percent of polymerized acrylonitrile and up to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith, a solvent therefor, and an inhibiting agent containing substantially equal proportions by weight of formaldehyde, a compound having the gen eral formula, v

wherein R is selected from the group consisting of sodium and cresyl radicals; and an inorganic acid having an ionization constant greater than 1 x 10"; and heating the mixture to form a homogeneous solution.

15. The method as defined in claim 14 wherein the polymer is a copolymer containingfrom 80 to 98 percent of acrylonitrile and from 2 to 20 percent of another polymerizable mono-olefinic monomer copolymerizable therewith.

16. The method as defined in claim 14 wherein the polymer is a blend of 80 to 99 percent of (A) a copolymer containing 90 to 98 percent of acrylonitrile and 2 to 10 percent of vinyl acetate and 1 to 20 percent of (B) a copolymer containing 10 to percent of acrylonitrile and 30 to 90 percent of 2-methyl-5-vinylpyridine.

17. The method as defined in claim 14 wherein the polymer is polyacrylonitrile.

18. A method for preparing a new composition of matter comprising mixing a polymer blend of to 99 1 percent of (A) a copolymer containing to 98 percent of acrylonitrile and 2 to 10 percent of vinyl acetate and 1 to 20 percent of (B) a copolymer containing 10 to 70 percentof acrylonitrile and 30 to 90 percent of Z-methyl- 5-vinylpyridine, a solvent therefor, and 0.3 to 15 percent, based on the total weight of the polymer, of an in hibiting agent, said inhibiting agent containing substantially equal proportions by weight of formaldehyde, a compound having the general formula, V

i Roi =o R wherein R is selected from the group consisting of sodium and cresyl radicals; and sulfuric acid; and heating the mixture to a temperature in a range of 25 C. to the boiling point of said mixture to form a homogeneous solution.

References Cited in the file of this patent UNITED STATES PATENTS 2,502,030 Scheiderbauer Mar. 28, 1950 2,676,940 I Kenyon Apr. 27, 1954v 

1. A NEW COMPOSITION OF MATTER COMPRISING A POLYMER CONTAINING AT LEAST 80 PERCENT OF POLYMERIZED ACRYLONITRILE AND UP TO 20 PERCENT OF ANOTHER POLYMERIZABLE MONO-OLEFINIC MONOMER COPOLYMERIZABLE THEREWITH, A SOLVENT THEREFOR, AND AN INHIBINTING AGENT CONTAINING A SUBSTANTIALLY EQUAL PROPORTIONS BY WEIGHT OF FORMALDEHYDE, A COMPOUND HAVING THE GENERAL FORMULA 